Synthetic pathway of a Cu$_2$ZnSnS$_4$ powder using low temperature annealing of nanostructured binary sulfides

Cost-effective route to quaternary Cu$_2$ZnSnS$_4$ nanostructured powder fabrication was developed by utilizing a two-step approach. In the first stage, nanostructured binary sulfides Cu$_2$S, ZnS, and SnS were synthesized by chemical bath deposition. In the second stage, ternary sulfide Cu$_2$ZnSnS$_4$ was obtained by low-temperature annealing of binary sulfides' mixtures at 70 and 300$^\circ$ C. The compounds obtained on both stages were investigated by X-ray diffraction, scanning electron microscopy, optical absorbance and Raman spectroscopy. On the basis of our findings, we established that Cu$_2$ZnSnS$_4$ phase has already formed at 300$^\circ$ C. The synthetic pathway revealed in this work allows reducing the temperature of Cu$_2$ZnSnS$_4$ synthesis and as a result, offers the possibility of reducing the manufacturing costs.